1. An 1760 kg car is moving to the right at a constant velocity of 2.94 m/s.
(a) What is the net force on the car?
(b) What would be the net force on the car if it were moving to the left?
2.A freight train has a mass of 6 107 kg. If the locomotive can exert a constant pull of 15 105 N, how long would it take to increase the speed of the train from rest to 85 km/h?
3. Pick the statements below that describe Newton's Second Law. You must pick all the correct answers to get credit.
-If mass increases and force stays the same, acceleration decreases
-Law of inertia
-An object in motion needs a force to keep it moving
-If force increases and mass stays the same, acceleration increases
-For every action, there is an equal but opposite reaction
-An object in motion remains in motion unless acted on by an outside force
-Net force equals zero in equilibrium
-Sum of all forces equals zero in equilibrium
-For every action, there is a reaction in the same direction
-An object at rest remains at rest unless acted on by an outside force
-Fnet=m*a
4.Pick the situations below that fit Newton's Second Law. You must pick all the correct answers to get credit.
-A crate is pushed forward with 60N while friction acts backward with 60N of force
-An airplane is in equilibrium
-The net force on a helicopter is 3,000N
-The forces on a skateboarder are balanced
-A dog pushes down on the ground with 16N of force and the ground pushes up on the dog with 16N of force
-A car accelerates forward at 1.6m/s²
-The forces on an arrow are unbalanced
-A bicycle pushes down on the ground with 67N of force and the ground pushed down on the bicycle with 67N of force.
-A box is pushed forward with 900N and friction acts backwards with 400N of force
-A truck drives at a constant speed of 100m/s
5.Pick the statements below that describe Newton's First Law. You must pick all the correct answers to get credit.
-An object at rest remains at rest unless acted on by an outside force
-If mass increases and force stays the same, acceleration decreases
-Law of inertia
-An object in motion remains in motion unless acted on by an outside force
-For every action, there is an equal but opposite reaction
-For every action, there is a reaction in the same direction
-Sum of all forces equals zero in equilibrium
-An object in motion needs a force to keep it moving
-If force increases and mass stays the same, acceleration increases
-Net force equals zero in equilibrium
-Fnet=m*a
6.Pick the situations below that fit Newton's First Law. You must pick all the correct answers to get credit.
-A crate is pushed forward with 90N while friction acts backward with 90N of force
-The net force on a helicopter is 5,000N
-A box is pushed forward with 700N and friction acts backwards with 400N of force
-A dog pushes down on the ground with 31N of force and the ground pushes up on -the dog with 31N of force
-A car accelerates forward at 3.7m/s²
-The forces on a skateboarder are balanced
-A bicycle pushes down on the ground with 66N of force and the ground pushed down on the bicycle with 66N of force.
-A truck drives at a constant speed of 10m/s
-An airplane is in equilibrium
-The forces on an arrow are unbalanced
1. (a) The net force on the car can be calculated using Newton's second law, which states that force equals mass multiplied by acceleration. Since the car is moving at a constant velocity and not accelerating, the net force on the car is zero.
(b) If the car were moving to the left with the same velocity, the net force would still be zero. The direction of motion does not affect the net force as long as the velocity remains constant.
2. To calculate the time it would take to increase the speed of the train from rest to 85 km/h, we need to use the equation:
Acceleration = (Net force)/(Mass)
Since the train is initially at rest, the net force will be equal to the force exerted by the locomotive.
Acceleration = (Force)/(Mass)
Acceleration = (15 * 10^5 N)/(6 * 10^7 kg)
Acceleration = 0.025 m/s^2
Now, we can use the equation of motion:
Final velocity^2 = Initial velocity^2 + 2 * Acceleration * Distance
Converting the final velocity to m/s:
Final velocity = 85 km/h = 85 * 1000 m/3600 s ≈ 23.6 m/s
Since the train starts from rest (initial velocity = 0), the equation becomes:
(23.6 m/s)^2 = 2 * 0.025 m/s^2 * Distance
Solving for the distance:
Distance = (23.6 m/s)^2 / (2 * 0.025 m/s^2)
Distance ≈ 55624 m
Now, we can calculate the time using the equation:
Time = Distance / Final velocity
Time = 55624 m / 23.6 m/s
Time ≈ 2357.28 s
Therefore, it would take approximately 2357.28 seconds for the train to increase its speed from rest to 85 km/h.
3. The statements that describe Newton's Second Law are:
- If mass increases and force stays the same, acceleration decreases
- If force increases and mass stays the same, acceleration increases
- Fnet = m * a
1. (a) To find the net force on the car, we can use Newton's second law, which states that net force is equal to mass multiplied by acceleration. Since the car is moving at a constant velocity, its acceleration is zero. Therefore, the net force on the car is also zero.
(b) If the car were moving to the left with the same constant velocity of 2.94 m/s, the net force would still be zero. The direction of the velocity does not affect the net force as long as the velocity is constant.
2. To find the time it takes to increase the speed of the train from rest to 85 km/h, we can use the equation of motion: v = u + at, where u is the initial velocity, v is the final velocity, a is the acceleration, and t is the time. In this case, the initial velocity (u) is 0 m/s, the final velocity (v) is 85 km/h (which needs to be converted to m/s), and the acceleration (a) can be calculated using Newton's second law (F = ma) by dividing the force (15 x 10^5 N) by the mass of the train (6 x 10^7 kg). By rearranging the equation v = u + at, we can solve for t, which will give us the time required to reach the final velocity.
3. The statements that describe Newton's Second Law are:
- If mass increases and force stays the same, acceleration decreases
- If force increases and mass stays the same, acceleration increases
- Fnet = ma, where Fnet is the net force, m is the mass, and a is the acceleration.
4. The situations that fit Newton's Second Law are:
- A crate is pushed forward with 60N while friction acts backward with 60N of force (force of friction opposes the applied force)
- A car accelerates forward at 1.6m/s² (acceleration is produced by a net force)
- A box is pushed forward with 900N and friction acts backwards with 400N of force (net force is the difference between the applied force and the force of friction)
5. The statements that describe Newton's First Law are:
- An object at rest remains at rest unless acted on by an outside force
- An object in motion remains in motion unless acted on by an outside force
- Law of inertia
6. The situations that fit Newton's First Law are:
- A crate is pushed forward with 90N while friction acts backward with 90N of force (no change in motion as the applied force is balanced by the force of friction)
- The forces on a skateboarder are balanced (no net force, so no change in motion)
- A truck drives at a constant speed of 10m/s (constant velocity indicates no net force)
- An airplane is in equilibrium (balanced forces, no change in motion)